I think one very serious problem with someone paying for features, is determining if a certain change actually does what the person wanted. In the commercial wo

I think one very serious problem with someone paying for features, is determining if a certain change actually does what the person wanted. In the commercial world the client decides that software is good enough for them by paying for that software (that already exists). But say if I want a certain feature from an open source project, and decide to pay for it, and someone writes a sloppy fix which does almost that and argues I should pay them, how is the conflict resolved? The developer has already used his time, so if I decide not to pay, there is a good chance the implementation is included anyway later. One would need the same kind of management as is used for custom software projects, but that is way too heavy for small individual features.